Class File

const file = bucket.file("text.txt");
file.createReadStream();

This works by loading chunks of the stream, upto B2.partSize, into memory. If the stream has less than or equal to that many bytes, a single-part upload will be attempted.

Otherwise, a multi-part upload will be attempted by loading up-to b2.partSize bytes of the stream into memory at a time.

const file = bucket.file("example");
const stream = file.createWriteStream();
stream.on("error", (err) => {
  // handle the error
  // note that retries are automatically attempted before errors are
  // thrown for most potentially recoverable errors, as per the B2 docs.
})
stream.on("finish", (err) => {
  // upload done, the file instance has been updated to reflect this
})
res.body.pipe(stream);

When stating a file without its fileId, this is a Class C transaction See https://www.backblaze.com/b2/cloud-storage-pricing.html

throws

BackblazeLibraryError.FileNotFound When a file is not found by name.